Arthur Ashton’s Serendipitous Invention of Optical Tweezers

(p. B11) Arthur Ashkin, a physicist who was awarded a 2018 Nobel Prize for figuring out how to harness the power of light to trap microscopic objects for closer study, calling his invention optical tweezers, died on Sept. 21 [2020] at his home in Rumson, N.J.

. . .

Dr. Ashkin’s discovery was serendipitous.

In 1966, he was head of the laser research department at Bell Labs, the storied New Jersey laboratory founded by the Bell Telephone Company in 1925, when he went to a scientific conference in Phoenix. There, in a lecture, he heard two researchers discuss something odd that they had found while studying lasers, which had been invented six years earlier: They had noticed that dust particles within the laser beams careened back and forth. They theorized that light pressure might be the cause.

Dr. Ashkin did some calculations and concluded that this was not the cause — it was most likely thermal radiation. But his work reignited a childhood interest in the subject of light pressure.

Light pushes against everything, including people, because it comprises tiny particles called photons. Most of the time the pressure is utterly insignificant; people, for one, feel nothing. But Dr. Ashkin thought that if objects were small enough, a laser might be used to push them around.

. . .

Then, in 1986, he and several colleagues, notably Steven Chu, achieved the first practical application of optical tweezers when they sent a laser through a lens to manipulate microscopic objects. Their results were published in another paper in Physical Review Letters. Dr. Chu began using the tweezers to cool and trap atoms, a breakthrough for which he was awarded a one-third share of the Nobel Prize in Physics in 1997.

Dr. Ashkin, it was clear, was irked that the Nobel committee had not recognized his foundational work in awarding the prize. But he had already begun to use the tweezers for a different purpose: trapping live organisms and biological material.

Other scientists thought this application would not work, as he explained in an interview with the Nobel Institute after he was awarded the prize in 2018.

“They used light to heal wounds, and it was considered to be deadly,” he said. “When I described catching living things with light, people said, ‘Don’t exaggerate, Ashkin.’”

. . .

Dr. Ashkin was awarded one-half the 2018 physics prize, . . . . In so doing he became, at 96, the oldest recipient of a Nobel Prize at the time.

. . .

Dr. Ashkin’s retirement from Bell Labs did not stop him from continuing his research. When he received word of his Nobel Prize, he was working on a project in his basement to improve solar energy collection. Asked if he was going to celebrate, he said: “I am writing a paper right now. I am not about celebrating old stuff.”

For the full obituary, see:

Dylan Loeb McClain. “Arthur Ashkin, 98, Dies; Nobel-Winning Physicist.” The New York Times (Tuesday, September 29, 2020): B11.

(Note: ellipses, and bracketed year, added.)

(Note: the online version of the obituary was updated Oct. 5, 2020, and has the title “Arthur Ashkin, 98, Dies; Nobel Laureate Invented a ‘Tractor Beam’.”)

The essay about Aoyagi mentioned above is:

Severinghaus, John W. “Takuo Aoyagi: Discovery of Pulse Oximetry.” Anesthesia & Analgesia 105, no. 6 (Dec. 2007): S1-S6.

“Greatness in Science Often Comes From the Well-Prepared Mind Turning a Chance Observation Into a Major Discovery”

(p. 27) Takuo Aoyagi, a Japanese engineer whose pioneering work in the 1970s led to the modern pulse oximeter, a lifesaving device that clips on a finger and shows the level of oxygen in the blood and that has become a critical tool in the fight against the novel coronavirus, died on April 18 [2020] in Tokyo.

. . .

Mr. Aoyagi’s contribution to medical science was built on decades of innovation and invention. In an essay about Mr. Aoyagi, John W. Severinghaus, a professor emeritus of anesthesia at the University of California, San Francisco, wrote in 2007 that Mr. Aoyagi’s “dream” had been to detect oxygen saturation levels without having to draw blood.

. . .

But he soon ran into a problem. Blood does not flow smoothly like an open tap, but pulses through the body irregularly, thus preventing an accurate recording of dye levels. The problem, however, turned out to be an opportunity. By devising a mathematical formula to correct for this “pulsatile noise,” he created a device that measured oxygen levels with greater accuracy than before.

“Greatness in science, often, as here, comes from the well-prepared mind turning a chance observation into a major discovery,” Dr. Severinghaus wrote.

For the full obituary, see:

John Schwartz and Hikari Hida. “Takuo Aoyagi, 84; Invented Medical Device.” The New York Times, First Section (Sunday, May 3, 2020): 27.

(Note: ellipses, and bracketed year, added.)

(Note: the online version of the obituary was updated June 20, 2020, and has the title “Takuo Aoyagi, an Inventor of the Pulse Oximeter, Dies at 84.”)

The essay about Aoyagi mentioned above is:

Severinghaus, John W. “Takuo Aoyagi: Discovery of Pulse Oximetry.” Anesthesia & Analgesia 105, no. 6 (Dec. 2007): S1-S6.

“You Can’t Wait for Somebody to Make a Giant Study”

(p. A6) In April [2020], researchers published an article in the Journal of the American Medical Association suggesting many Covid-19 patients with respiratory distress might require a different treatment approach than typically used for ARDS.

. . .

Maurizio Cereda, an anesthesiologist and head of the surgical ICU at the Hospital of the University of Pennsylvania, said doctors normally use standardized tables to match the level of oxygen in the blood with the amount of PEEP needed. Penn tends to use a table with lower PEEP values, he said, but even those lower levels seem to damage the lungs of some of his Covid-19 patients. As a result, he disregards the table entirely at times, he said, even though some in his institution disagree with his approach.

“You can’t wait for somebody to make a giant study,” Dr. Cereda said. “You are alone with your clinical observation. A lot of people don’t feel comfortable with that because they want to have big guidelines. People seem to be afraid they’re going to do something wrong.”

. . .

At Maimonides Medical Center in Brooklyn, critical-care and emergency-medicine doctor Cameron Kyle-Sidell said he was initially seeing much higher mortality rates from Covid19 patients on ventilators than he would have expected from classic ARDS, possibly because physicians were sticking to PEEP levels used to treat traditional ARDS.

“There are people who are treating this the way they would have treated any other ARDS,” he said. “Then there’re people on the flip side—and I am on that flip side—that think you should treat it as a different disease than we treated in the past.”

For the full story, see:

Sarah Toy and Mark Maremont. “Doctors Split on Best Way To Treat Coronavirus Cases.” The Wall Street Journal (Thursday, July 2, 2020): A6.

(Note: ellipses, and bracketed year, added.)

(Note: the online version of the story has the date July 1, 2020, and has the title “Months Into Coronavirus Pandemic, ICU Doctors Are Split on Best Treatment.” The online version quoted above includes a couple of added sentences quoting Dr. Cereda, beyond the single sentence quoted in the print version.)

Natural Experiments Are Equal to Randomized Double-Blind Clinical Trials in Showing Causality

(p. B6) . . . randomized controlled trials are the gold standard in medicine. Using randomization (by, say, flipping a coin to assign patients to a new treatment or not) is the best way to determine whether treatments work.

Unfortunately, randomized trials take time — which is a problem when doctors need answers now. So doctors and public health officials have been turning to available real-world data on patient outcomes and trying to make sense of them.

. . .

“Large-scale randomized evaluations have been less common in economics, prioritizing the need for economists to identify often creative but sometimes narrow natural experiments to estimate the causal effects of treatments,” said Amitabh Chandra, an economist at the Harvard Business School and the Kennedy School of Government.

Ashish Jha, recently appointed the dean of the Brown University School of Public Health, said that while “natural experiments have causal interpretations, typical associational studies in medicine do not, which may make some medical researchers less comfortable interpreting the results.”

. . .   Most doctors can relate to recent comments by the Food and Drug Administration director Stephen Hahn in last week’s congressional pandemic hearing. “In a rapidly moving situation like we have now with Covid-19,” he said, decisions are made “based on the data that’s available to us at the time.”

For the full commentary, see:

Anupam B. Jena and Christopher M. Worsham. “THE UPSHOT; What Coronavirus Researchers Can Learn From Economists.” The New York Times (Thursday, July 2, 2020): B6.

(Note: ellipses added.)

(Note: the online version of the commentary has the date June 30, 2020, and has the same title as the print version.)

Open Offices Reduce Productivity and Spread Diseases

(p. B4) When historians of the early 21st century look back on the pre-Covid era, one of the absurdities they might highlight is the vogue for gigantic, open-plan offices. The apotheosis of this trend of breaking down barriers between co-workers must surely be Facebook Inc.’s 433,555-square-foot Frank Gehry-designed open-plan office at its headquarters in Menlo Park, Calif. Opened in 2015, it’s now a ghost town, a monument to offices vacated by the pandemic.

Cramming cavernous spaces with as many desks as they could hold might have increased serendipitous interactions, but it almost certainly reduced productivity and helped spread communicable diseases, including coronavirus.

. . .

Cue the “dynamic workplace,” a pivot away from the open plan, built on the idea that with fewer employees coming to work on any given day, offices can offer them more flexibility of layout and management.

While open offices and dynamic workplaces share similar components—privacy booths and huddle rooms to escape the hubbub, cafe-like networking spaces, etc.—they’re philosophically distinct. One is intended to be a place where people come (at least) five days a week, and get most of their work done on site. The other is planned for people rotating in and out of the office, on flexible schedules they have more control over than ever.

. . .

Research on hot-desking in office spaces, for example—where employees give up a dedicated space in favor of first-come-first-serve seating—finds that it decreases socialization and trust. This happens because employees figure they might never again see the person they sit next to on a given day, says Dr. Sander. In other studies, employees complain they can’t find their colleagues, that it’s a hassle to find a new spot to work every day, and that such arrangements ignore humans’ innate territoriality and desire to make a space their own.

For the full commentary, see:

Christopher Mims. “Goodbye, Open Office. Hello, ‘Dynamic Workplace.” The Wall Street Journal (Saturday, September 12, 2020): B4.

(Note: ellipses added.)

(Note: the online version of the commentary has the same date and title as the print version.)

How “Blind” Is a Double-Blind Trial When Volunteers Know the Side-Effects of the Vaccine?

(p. A8) George Washington University had vaccinated 129 people since its share of the trials started. I would be No. 130. Altogether, Moderna planned to enroll 30,000 people in its trial. Half would be given the actual vaccine and half would get the placebo. The protocol called for two shots spaced a month apart.

Finally, it was time for my injection, which is when things got a little weird.

“We have to leave you now, because this is a double-blind study and we are blinded,” Dr. Malkin said. “You’ve been randomized.”

Before I could ask her to translate what she had just said, she was gone, and two nurses arrived with my vaccine. The first nurse left, and the second nurse, Linda Witkin, asked whether I was right-handed or left-handed, then proceeded to inject my right arm.

“Which one are you giving me, the vaccine or the placebo?” I asked. She gave me a look, clearly not pleased with my questioning.

. . .

With the Moderna trial, the side effects reported so far have been typical: fever, chills, muscle and joint soreness.

. . .

The night after my shot, I took my temperature: 97.5. I felt under my arms for glandular swelling and felt only mild joint pain.

. . .

“You all gave me the placebo, didn’t you?” I demanded of Dr. Diemert on Wednesday, during my one-week checkup. “I cannot believe I went through all of this and got the placebo.”

He told me that the actual vaccine shot was more “viscous” than the placebo, which was why neither he nor Dr. Malkin could be in the room when I got it, because they would have been able to easily determine. And so he really couldn’t answer because the double-blind program is meant to protect doctors like him from patients like me. He said I wasn’t to badger Ms. Witkin, if I ever even saw her again. He also said that most people reacted more to the second shot than the first one.

I texted the peanut gallery, “I feel no different.”

For the full story, see:

Helene Cooper. “From Reporting on Ebola to Being a Volunteer in a Covid-19 Vaccine Trial.” The New York Times (Saturday, September 12, 2020): A8.

(Note: ellipses added.)

(Note: the online version of the story has the date Sep. 11, 2020, and has the title “Covering Ebola Didn’t Prepare Me for This: I Volunteered for the Covid-19 Vaccine Trial.”)

Quick, Less Precise, but Repeated, Covid-19 Tests Can Be Better Than Slow Precise Tests

(p. A1) Public health experts are increasingly calling for a shift in thinking about Covid-19 testing: It is better to get fast, frequent results that are reasonably accurate than more precise results after dayslong delays.

. . .

Covid-19 tests that don’t require a lab tend to be less sensitive than “gold standard” laboratory-based tests, meaning they are likely to miss more cases. But many public health experts now say that repeat testing can make up for the loss of sensitivity, and such testing could quickly identify the most infectious people and help bring transmission to heel as workplaces and schools resume in-person operations and as influenza season looms.

. . .

(p. A6) “When we looked ahead, we realized we needed a paradigm shift from the still-needed diagnostic tests to the screening tests,” said Jonathan Quick, managing director for pandemic response, preparedness and prevention at the Rockefeller Foundation, which released a report in July [2020] calling for a massive scale-up in quick, cheap tests for Covid-19 screening. “As a practical matter, that meant making much more of a new kind of test,” Dr. Quick said.

Most Covid-19 diagnostic testing in the U.S. is processed in laboratories and uses a technique called rt-PCR that searches for the virus’s genetic material and amplifies it. The tests are incredibly sensitive but expensive to run, and the process often requires shipping samples from a test site to a lab.

. . .

“I think there’s a sense of desperation that we need to do something else,” Ashish Jha, dean of Brown University’s School of Public Health, said at a media briefing in August [2020].

. . .

Antigen tests are better at identifying cases when people have more virus in their system—meaning they will likely find people when they are most infectious, said Michael Mina, an epidemiologist at the Harvard T.H. Chan School of Public Health and an advocate of low-cost, widely available at-home testing that can be done on a paper strip.

. . .

The FDA also has said that rapid tests should have comparable accuracy to PCR diagnostic tests—a requirement that some public health specialists and companies say is overly stringent for surveillance testing.

An FDA official noted sensitivity rates lower than PCR might be acceptable, depending on how the test results are used. The agency has allowed for antigen tests with a sensitivity rate of 80% or better, the official said. “You can even have lower than 80% sensitivity” if it is a recurring or serial test.

For the full story, see:

Brianna Abbott, and Thomas M. Burton. “Speed Over Precision Favored in Covid Tests.” The Wall Street Journal (Wednesday, September 9, 2020): A1 & A6.

(Note: ellipses, and bracketed year, added.)

(Note: the online version of the story has the date Sep. 8, 2020, and has the title “Public Health Officials Pursue Covid-19 Tests That Trade Precision for Speed.” Where there are differences between the print and online versions, the passages above follow the online version.)

The report by The Rockefeller Foundation mentioned above is:

The Rockefeller Foundation. “National Covid-19 Testing & Tracing Action Plan.” Thurs., July 16, 2020.

Randomized Controlled Trials Can Obscure “Nuances and Complexities”

(p. A17) You’ve probably heard of the “gold standard”—randomized controlled trials—for evaluating new pharmaceutical therapies, including for Covid-19. Many treatments that showed promise in other studies have turned up muddy results in randomized controlled trials. But that doesn’t mean they’re necessarily ineffective. Doctors and regulators need to consider the totality of medical evidence when treating patients.

. . .

“Randomized trials for some purposes is the gold standard, but only for some purposes,” Harvard’s Donald Berwick, a former health adviser to President Barack Obama, said in an interview with GNS Health Care CEO Colin Hill in 2013. “Context does matter. We’re learning in a very messy world, and the context that neatens up that world may make it hard to know how to manage in the real world.”

. . .

As Thomas Frieden, who directed the Centers for Disease Control and Prevention under Mr. Obama, wrote in a 2017 New England Journal of Medicine article: “Elevating RCTs at the expense of other potentially highly valuable sources of data is counterproductive.” Such limitations affect their use for “urgent health issues, such as infectious disease outbreaks.” He added: “No study design is flawless, and conflicting findings can emerge from all types of studies.”

. . .

Some experts have dismissed the antimalarial hydroxychloroquine, or HCQ, even though more than a dozen observational studies have found it beneficial. A retrospective observational study of Covid-infected nursing-home residents in France, for instance, found those treated with HCQ and azithromycin were 40% less likely to die.

But a few randomized controlled trials found no benefit. A Spanish randomized trial of HCQ for prophylaxis found it didn’t reduce risk of illness among a large group of people exposed in nursing homes, households and health-care settings. Yet two-thirds of the subjects “reported routine use of masks at the time of exposure,” so they were probably less likely to be infected. Nursing-home residents, who may be less likely to wear masks, were 50% less likely to become sick if they took HCQ. But this finding was statistically insignificant, because the trial included only 293 residents.

. . .

Another problem with Covid-19 randomized trials: Patients at different stages of an illness are often assigned the same dosage. Trials don’t reveal differences in how patients respond to a drug at different dosages or illness severity.

Observational studies can do so. Consider a large study by the Mayo Clinic, which found no overall benefit among patients who received a higher-antibody convalescent plasma versus a lower one. Yet the researchers reported a 37% reduction in mortality among patients under 80 who weren’t on a ventilator and received a high-antibody plasma within three days of hospitalizations.

A randomized trial might have obscured these nuances and complexities, denying doctors important information about treatment options. Randomized controlled trials can yield important insights, but it is a medical mistake and a disservice to patients to dismiss other types of evidence.

For the full commentary, see:

Allysia Finley. “Medical Research’s Cross of ‘Gold’ Imperils Covid Treatments.” The Wall Street Journal (Wednesday, September 9, 2020): A17.

(Note: ellipses added.)

(Note: the online version of the commentary has the date Sep. 8, 2020, and has the same title as the print version.)

The review article by Frieden mentioned above is:

Frieden, Thomas R. “Evidence for Health Decision Making — Beyond Randomized, Controlled Trials.” New England Journal of Medicine 377, no. 5 (Aug. 3, 2017): 465-75.

“All You Need Is a Pair of Eyes”

(p. 1) MUNICH — Dr. Camilla Rothe was about to leave for dinner when the government laboratory called with the surprising test result. Positive. It was Jan. 27 [2020]. She had just discovered Germany’s first case of the new coronavirus.

But the diagnosis made no sense. Her patient, a businessman from a nearby auto parts company, could have been infected by only one person: a colleague visiting from China. And that colleague should not have been contagious.

The visitor had seemed perfectly healthy during her stay in Germany. No coughing or sneezing, no signs of fatigue or fever during two days of long meetings. She told colleagues that she had started feeling ill after the flight back to China. Days later, she tested positive for the coronavirus.

. . .

Dr. Rothe and her colleagues were among the first to warn the world. But even as evidence accumulated from other scientists, leading health officials expressed unwavering confidence that symptomless spreading was not important.

In the days and weeks to come, politicians, public health officials and rival academics disparaged or ignored the Munich team. Some actively worked to undermine the warnings at a crucial moment, as the disease was spreading unnoticed in French churches, Italian soccer stadiums and Austrian ski bars. A cruise ship, the Diamond Princess, would become a deadly harbinger of symptomless spreading. Continue reading ““All You Need Is a Pair of Eyes””

Volunteer “Challenge Trials” Could Speed Covid-19 Vaccine

(p. A10) It’s a controversial idea: Intentionally infect people with the virus that causes Covid-19 to test the effectiveness of a potential vaccine.

The approach is called a human challenge trial, and it’s not the usual way a vaccine is tested. More commonly, researchers track thousands of people, some of whom receive a vaccine, and others a placebo, and then see who becomes infected in the natural course of their lives. It’s a slower process, but poses fewer risks than deliberately infecting people after they’ve received a vaccine.

But some scientists now argue the risks of such a challenge trial are worth taking if it could potentially speed the development of a vaccine. Three groups of health experts have recently published articles advocating for the idea.

. . .

A company in London called hVIVO that specializes in human challenge trials is “very actively looking into how we could build a Covid-19 challenge study to help speed up the world wide development of an effective vaccine,” said Cathal Friel, executive chairman of Open Orphan, a clinical trials company that acquired hVIVO earlier this year. He says at least 10 pharmaceutical companies have already expressed interest in their potentially conducting a challenge trial of their vaccine candidates.

Ssome people say they would be willing to volunteer. Josh Morrison, a 34 year old in New York City, has started a group called 1Day Sooner where people can express interest in participating in a future challenge trial for Covid-19. So far around 16,000 people from more than 100 countries have signed up, including him, despite the fact that he donated a kidney in 2011.

“Obviously I would prefer not to get Covid-19,” he says. “But I also felt like this was a chance to be part of saving thousands or even hundreds of thousands of lives. And I felt so powerless at the time that being able to take action and do something meaningful was a strong motivator to me.”

For the full commentary, see:

Sumathi Reddy. “YOUR HEALTH; One Idea to Speed a Vaccine: Deliberately Infect People.” The Wall Street Journal (Tuesday, May 12, 2020): A10.

(Note: ellipsis added.)

(Note: the online version of the commentary was the date May 11, 2020 and has the title “YOUR HEALTH; One Idea for Speeding a Coronavirus Vaccine: Deliberately Infecting People.” Where the print and online versions differ, the passages quoted above follow the print version. For instance, the online version says that about “15,000” people have signed up.)

Mainstream Science, and Governments, Rejected Early Evidence of Symptomless Transmission

(p. 1) MUNICH — Dr. Camilla Rothe was about to leave for dinner when the government laboratory called with the surprising test result. Positive. It was Jan. 27 [2020]. She had just discovered Germany’s first case of the new coronavirus.

But the diagnosis made no sense. Her patient, a businessman from a nearby auto parts company, could have been infected by only one person: a colleague visiting from China. And that colleague should not have been contagious.

The visitor had seemed perfectly healthy during her stay in Germany. No coughing or sneezing, no signs of fatigue or fever during two days of long meetings. She told colleagues that she had started feeling ill after the flight back to China. Days later, she tested positive for the coronavirus.

. . .

Dr. Rothe and her colleagues were among the first to warn the world. But even as evidence accumulated from other scientists, leading health officials expressed unwavering confidence that symptomless spreading was not important.

In the days and weeks to come, politicians, public health officials and rival academics disparaged or ignored the Munich team. Some actively worked to undermine the warnings at a crucial moment, as the disease was spreading unnoticed in French churches, Italian soccer stadiums and Austrian ski bars. A cruise ship, the Diamond Princess, would become a deadly harbinger of symptomless spreading.

. . .

(p. 10) Though estimates vary, models using data from Hong Kong, Singapore and China suggest that 30 to 60 percent of spreading occurs when people have no symptoms.

. . .

After two lengthy phone calls with the woman, doctors at the Robert Koch Institute were convinced that she had simply failed to recognize her symptoms. They wrote to the editor of The New England Journal of Medicine, casting doubt on Dr. Rothe’s findings.

Editors there decided that the dispute amounted to hairsplitting. If it took a lengthy interview to identify symptoms, how could anyone be expected to do it in the real world?

“The question was whether she had something consistent with Covid-19 or that anyone would have recognized at the time was Covid-19,” said Dr. Eric Rubin, the journal’s editor.

“The answer seemed to be no.”

The journal did not publish the letter. But that would not be the end of it.

. . .

On Monday, Feb. 3, the journal Science published an article calling Dr. Rothe’s report “flawed.” Science reported that the Robert Koch Institute had written to the New England Journal to dispute her findings and correct an error.

. . .

Dr. Rothe’s report quickly became a symbol of rushed research. Scientists said she should have talked to the Chinese patient herself before publishing, and that the omission had undermined her team’s work. On Twitter, she and her colleagues were disparaged by scientists and armchair experts alike.

“It broke over us like a complete tsunami,” Dr. Hoelscher said.

. . .

If Dr. Rothe’s paper had implied that governments might need to do more against Covid-19, the pushback from the Robert Koch Institute was an implicit defense of the conventional thinking.

Sweden’s public health agency declared that Dr. Rothe’s report had contained major errors. The agency’s website said, unequivocally, that “there is no evidence that people are infectious during the incubation period” — an assertion that would remain online in some form for months.

French health officials, too, left no room for debate: “A person is contagious only when symptoms appear,” a government flyer read. “No symptoms = no risk of being contagious.”

. . .

(p. 11) Dr. Rothe, . . ., was shaken. She could not understand why much of the scientific establishment seemed eager to play down the risk.

“All you need is a pair of eyes,” she said. “You don’t need rocket-science virology.”

. . .

While public health officials hesitated, some doctors acted. At a conference in Seattle in mid-February, Jeffrey Shaman, a Columbia University professor, said his research suggested that Covid-19’s rapid spread could only be explained if there were infectious patients with unremarkable symptoms or no symptoms at all.

In the audience that day was Steven Chu, the Nobel-winning physicist and former U.S. energy secretary. “If left to its own devices, this disease will spread through the whole population,” he remembers Professor Shaman warning.

Afterward, Dr. Chu began insisting that healthy colleagues at his Stanford University laboratory wear masks. Doctors in Cambridge, England, concluded that asymptomatic transmission was a big source of infection and advised local health workers and patients to wear masks, well before the British government acknowledged the risk of silent spreaders.

The American authorities, faced with a shortage, actively discouraged the public from buying masks. “Seriously people — STOP BUYING MASKS!” Surgeon General Jerome M. Adams tweeted on Feb. 29.

. . .

By the end of the month [March 2020], the U.S. Centers for Disease Control announced it was rethinking its policy on masks. It concluded that up to 25 percent of patients might have no symptoms.

Since then, the C.D.C., governments around the world and, finally, the World Health Organization have recommended that people wear masks in public.

Still, the W.H.O. is sending confusing signals. Earlier this month, Dr. Van Kerkhove, the technical lead, repeated that transmission from asymptomatic patients was “very rare.” After an outcry from doctors, the agency said there had been a misunderstanding.

“In all honesty, we don’t have a clear picture on this yet,” Dr. Van Kerkhove said. She said she had been referring to a few studies showing limited transmission from asymptomatic patients.

Recent internet ads confused the matter even more. A Google search in mid-June for studies on asymptomatic transmission returned a W.H.O. advertisement titled: “People With No Symptoms — Rarely Spread Coronavirus.”

For the full story, see:

Matt Apuzzo, Selam Gebrekidan and David D. Kirkpatrick. “How the World Missed Covid’s Symptom-Free Carriers.” The New York Times, First Section (Sunday, June 28, 2020): 1 & 10-11.

(Note: ellipses, and bracketed dates, added.)

(Note: the online version of the story was updated June 27, 2020 and has the title “How the World Missed Covid-19’s Silent Spread.”)